Bob Shuman wrote:

I am looking at an older HP LaserJet 3P printer that will not print for a
friend. I do not have a service manual, but figured I would give this a
shot.

Symptoms: Plug in and power on the unit and it runs through its "05" self
test, then the green "on-line" light illuminates and the printer is in the
"ready" mode. If you try to send a job to the printer, the green light
flashes indicates it is receiving the file, but then the LCD panel indicates
an "error 52".

I disconnected the computer and attempted to print the self test page by
depressing the on-line (to go offline), then simultaneously depressing the
"alt" and "test" buttons. This then goes through the same 05 self test
followed by an 06 print test. At the conclusion of the 06 print test, you
can briefly hear the page feed motor and then the "52 Error" message is
illuminated.

I've checked the HP support web site and it indicates that the 52 is a
temporary internal error and that pressing the "continue" button may clear
the error. But, in my case, it tries to go through the test again, but you
get the same result.

Replace the scanner motor unit. The scanner motor units of thy
Laser-Printer-Types (LX-Type) have a heat problem.
Usually the chip and the PCB beneath is burnt.
I had the same problem with a Brother HL-4V (also LX-Type)
Replacing the unit is quite easy to do - only if you know which screws
to open getting to the 'core' of the printer ;-)

Michael